Field of the Invention
The present invention relates to an image reading apparatus that is provided with an automatic document feeder, and to an image forming apparatus equipped with the image reading apparatus.
Description of the Related Art
There is a known conventional image reading apparatus that reads an original image at a read position on a read glass while conveying originals stacked on an original tray one by one by an automatic document feeder (ADF). Such an image reading apparatus irradiates an original with light emitted from a light source when the original conveyed one by one by the ADF passes the reading position, and read the original by receiving reflected light from the original with an image pickup device like a CCD.
When an original is conveyed by the ADF, paper powder or toner sticking to the original may peel off and adhere to the read position on the read glass. When an original image is read in a state where dust, such as paper powder or toner, adheres to the read glass, a vertical streak appears in the read image at the position corresponding to the dust adhesion position because the dust obstructs light with which the original is irradiated.
Moreover, when a copying operation is performed in a state where a plurality of originals that are stacked by a user contain a blank-paper original, a copy of the blank-paper original will be formed by an image forming apparatus. In order to solve such a problem, an image forming apparatus that is provided with a blank-paper-detection function that determines whether an original is a blank-paper original at a time when an image reading apparatus reads the original is developed.
Incidentally, if it is determined whether an original is a blank-paper original in a state where a vertical streak appears in a read image due to dust adhering to an original reading position, the vertical streak may be determined as a print content. If the vertical streak is erroneously determined as a print content, the copying operation will be performed as-is for the blank-paper original. This wastes a copy paper sheet.
Thus there is a proposed apparatus that stops a reading operation or a copying operation and warns with a display unit, a voice message, etc. when dust adheres to an original reading position on a read glass. The apparatus restarts the operation only when the dust is removed by a user or a serviceman. See Japanese Laid-Open Patent Publication (Kokai) No. 2006-165980 (JP 2006-165980A). Since this apparatus stops the copying operation when dust adheres, the inconvenience that the copying operation is performed for a blank-paper original because the vertical streak is erroneously detected as the print content is canceled.
However, whenever dust adheres to the image reading position on the read glass, it is necessary to interrupt the reading operation or the copying operation and to clean according to the technique of the above-mentioned publication. Moreover, when a plurality of sheets, such as recycled paper sheet, of which particles of paper fiber are large and easily peel are conveyed, paper powder adheres to the read glass frequently. In such a case, it is necessary to clean the read glass frequently, which causes a problem that the image reading operation or the copying operation is interrupted on each occasion.